Molecular diagnostic testing has become an integral part of the evaluation of patients with metastatic colorectal cancer (CRC). Expanded mutational testing, such as next-generation sequencing (NGS), often identifies mutations with unclear clinical or prognostic implications. One such example is BRAF mutations that occur outside of codon 600 (non-V600BRAF mutations).
We conducted this multicenter, retrospective cohort study to characterize the clinical, pathologic, and survival implications of non-V600BRAF mutations in metastatic CRC. We pooled patients in whom non-V600BRAF mutations were identified from NGS databases at three large molecular genetics reference laboratories.
A total of 9,643 patients with metastatic CRC underwent NGS testing. We identified 208 patients with non-V600BRAF mutations, which occurred in 2.2% of all patients tested and accounted for 22% of all BRAF mutations identified. Cancers with non-V600BRAF mutations, compared with cancers with V600E BRAF (V600EBRAF) mutations, were found in patients who were significantly younger (58 v 68 years, respectively), fewer female patients (46% v 65%, respectively), and patients who had fewer high-grade tumors (13% v 64%, respectively) or right-sided primary tumors (36% v 81%, respectively).
Median overall survival was significantly longer in patients with non-V600BRAF-mutant metastatic CRC compared with those with both V600EBRAF-mutant and wild-type BRAF metastatic CRC (60.7 v 11.4 v 43.0 months, respectively; P , .001). In multivariable analysis, non-V600BRAF mutation was independently associated with improved overall survival (hazard ratio, 0.18; P , .001).
Non-V600BRAF mutations occur in approximately 2.2% of patients with metastatic CRC and define
a clinically distinct subtype of CRC with an excellent prognosis.